Radioreceiver



L. G. TATRO RADIORECEIVER Jan. 2, 1934.

1930 5 Sheets-Sheei'I l Filed March 29,

Jan. 2; 1934. L.. G. TATRO RADIORECEI-VER Filed March 29, 1930 5 Sheets-Sheet 2 .mi NJ @www #Smw @my m u W N%\m|\\ MW. \\I|W WWI J ,RWA NWlxs Y NAW Il l c l l l l l I l n 1 I I I l l I l IWW \\N\ mw, @1W 1 4 N'JI [www Q @mm W m /N|\ E @$16. 7/w7 LM Jan. 2, 1934. 'L G. TATRO RADIORECEIVER Filed March 29, 1930 3 Sheets-Sheet 3 i Patented Jan. 2, 1934 untreu; STATES 1,942,378 o nADIoRncEii/ER Lysle G.-Tatro, Decorah, Iowa, assigner to H. B.

Montgomery, Decorah, Iowa Application March 29, 1930. Serial 170.440,076

6 Claims.

I This invention relates to radio receiving sets and has among its aims to provide an improved receiving set` utilizing a battery supplied direct current system or the like, not only for current supply but also as a novel lament loop for intercepting radio frequency waves and transferring the same to the receiver through the filament of the radio frequency amplifier.

In the present specification` an illustrative embodiment of my invention is described with reference to a farm-power system of the 32-volt storage battery type, but throughout the present specification, the terms farm-power and farm-lighting are toV be understood as illustrative terms or catch phrases intended to designate equivalent systems capable of employment Y as an untuned "filament loop in accordance with my invention, including, for example, `direct current sources comprising primary or secondary batteries and commercial sources of such capability.; Y y

Particular objects and advantages of the invention will be Vapparent to those skilled in the art from the following description of the preferred embodiments of the'several features'of my invention shown in the accompanying ydrawings t'o'illustratethe same. Y

Referring to the drawings constitutingY ar part of this specicationt o l Fig. 1 is a diagrammatic representation of a completeradio receiving system embodying the several coordinated features of my invention;

Fig. 2 is a rear' elevation of a lament potential limiting and heat dissipating unit illustrativeof one embodiment of this feature of my invention;

and

Fig. 3 is a sectional pian View of the same taken atline 3-3 of Fig. 2. v i, Referring toFigs. la and lb of the drawing the receiving system therein shown comprises a specially adapted receiver circuit preferably employing three stagesY of radio-frequency amplification, (advantageously of the screen-grid direct current heated thermionicamplier tube type), a thermionic detector to convert the amplified radio-frequency current into audio-frequency current Vand an amplifier for the audio-frequency current, preferably comprising, in addition to one or more intermediate audio-frequency amplifiers,

a last stage audio-frequencyv amplifier of the push pull type. f

Throughout the showing of Figs. 1a and 1br the clrcuit is entirely independent of any earthing connection, the several grounded points throughout the diagram indicating electrical connections to shielding with which the set is provided.

Referring to Fig. ia, the circuit which I prefer to use, modified according to my invention, comprises a first radio-frequency coil connected at its opposite ends to the grid ll of the first thermionic amplifiery12, and to the receiverY shielding, as at 13.l The plate 14 of amplifier` 12 connects through primary winding 15 of the' radio-frequency transformer 16 with vthelead 17,

Awhich connects with the fB amplifier post ofthe B and C power unit hereinafter described. The-negative side of the' B source of this unit is connected to the shielding of the set and/.they

output circuit of the first thermionic amplifier is completed by way of the connection 18, connecting the shielding with the negative side of the filament 19 by'way of thevvariable resistor 20,V the function of which is described hereinafter. The input circuit of the first thermionic amplifier 12,` is also completed by this shield connection 18. VThe secondary 21 of the radio-frequency transformer 16, tuned bythe variable capacity 22 is connected to the grid and negative side of the filament of the second thermionic amplifier 23, thefoutput circuit of which includes vtheprimary 24 of radio-frequency transformer 25. The input circuit of the third radio-frequency amplifier 25 includes the secondary 27 of the radio-frequency transformer 25, and is tuned'by-means of the variable capacity 28, and the -output circuit of this'radio-frequency amplier 26 includes the primary 29-of radio-frequencyl transformer 30'. fr

The three screen vgrids of the -three radio-frequency amplifiers 12, 23 and 26 are interconnected without suppression and connected to a positive source of potential, conveniently the B detector post of my hereinafter described B and C power unit, by means of lead32.V f

The `secondary 33 of radio-frequency transformer is included in the input circuit of the thermionic'detector 34, `provided vwith the usual grid leak 35 and condenser 36,- andisl tunedyby means of a variable capacity 37. f

The variable tuning capacities 22, 28', andi37 are preferably interconnected for gang-tuning as indicated by the dotted lines 38.

The output circuit of the detector 34 includes a radio-frequency choke coil 39, the primary 40 of the audio-frequency transformer 41, andby connection with lead 32, connects throughthe detector section of my .B and C.- power unit with the shielding of `the set, the `by-passcondenser 42 bridging the radio-frequency choke coil 39, the audio-frequency.transformer primary 43 and the detector B power supply.

The C power supply, for negatively biasing the grid ofthe amplifier tube 44, which is connected between the C negative lead 52 and the set shieldingand the secondary 43 of the audio-frequency transformer 4l, are included in the input circuit of the first audio-frequency amplifier 44 (see Fig. 1b) and this input circuit is also preferably bridged by a phonograph pickup jack 45. The output of the audio-frequency amplifier includes the resistance unit 46, and is ,quentlydamages .the condensers 4and other partsv y32, 17, and 52, respectively.

coupled in any suitable known manner, as by the Clough system of coupling shown at 47, to the input sideof the push-pull amplifier stage, which includesxthe thermionic ampliiers 48 andk 48. The output of this push-pull amplifier stage is connected to a suitable loud speaker, preferably of the dynamic type and having a field winding' designed for operation at the ordinary directcurrent farm-power system voltage, usually about thirty-two volts. i

As shown in Fig. la, suitable condensers 49, 50 and 51 are inserted across. the detector and amplifier B power circuits and the C power circuit, as is well known in the art, by connecting them between the set shielding and the leads kAs thu'sfar described :the system, while novel inlsome "respects, inv general represents merely a modification of known circuits, and the particularly novel aspects of my invention will now bedescrlbed.

Thel disclosed embodiment of my improved system is particularly devised and adapted to be operated from battery supplied direct `current systemssuch as `the usual direct kcurrent farm power systems, generally comprisingfa thirty-V two volt storage battery and charging plant and from several hundred to several thousand feet of farm.power lines, usually Acomprising an un-y grounded system. I will first describe those parts of my inventionY which relate to the lighting of the-,filamentsA ofr the thermionic tubes farm-power system.

y Itfhas beenV proposed to connect the several 3 tubeflaments of a radio receiver in series and voperate lthem fromla relatively high jvoltage current source, but thistype of connection is not satisfactory'l either from a technicalor a= practicalstandpo'int. With such connection the burni ing out of ya single tube filament prevents any of the tubesffromlighting, thus making it diflicult to determine which tube hasburned out, and the controlcof volume vand the several ffilament currentsbecom'es technically involved. "ltfhas 'also been proposedtoconnect all the fi'llaments in parallel and use a single resistance in` the. .high voltageA line to reduce the voltage thereof to the operating voltage of thev several tubes.l Thiswproposal vis impracticable because the'burning out of one tube' results in increasing the voltage impressed :upon the other tube `ilaments andfrequently kcauses burning out `of the Whole set of tubes.` Furthermore, the `control of volume with suchen-arrangement cannot be accomplished in a Wholly satisfactory manner, and the concentrated heatV of the series resistor freof the set orxcabinet in which it ismounted. K

According to my invention, I provide for the reduction of line voltage to filament :lighting outnun'due concentration of heat by providing `a multiple-resistorV unit an illustrative` embodiment of which is `shown in detail in Figs..2 and 3 and generally indicated in Fig. l by the rnumeral v53.

Referring to Figs. 2 and` 3, this multiple-re'- v sistor unit preferably made up of a plurality of insulator tube type, and the assembly of they units 'and channels is effected by means such as boltszor rivets 5'6 passed through the channels from thevv `ofthe filament circuits may be varied by setting the movable clamps 61 at different positions along the resistance units. These clamps 61 will be set so that when the storage battery of the `farm-power system of given voltage rating is fully chargedl or at its highest voltage, the full operating voltage for the particular tube used will berimpressed thereon,.and it `will beobvious lthat the maximum of voltage thus allowed to be supplied tothe filament terminals will be .permanently determined and limited, for a given installation, insuring long tube life and satisfactory operation.

The provisions Vthusmade for varying the effective resistances, and thus the rfilament currents, vare advantageous `not only to allow a. standard unit to be used on farm lighting systems of different voltages, but also to provide for changingthe lament voltage to enable the use of 'thermionic tubesl utilizing various filament voltages.r Of course, if neither of these advantages is desired fixed*y resistance units may be substituted for above.

The multiple-resistor unit is of large area and may be permanently mounted either directly upon the chassis of the receiver, or with a layer of heat insulating material, or spacing washers, interposed. `The, attachment will vthus become a permanent part ofr the receiver and as the several resistors each give lforth only a small amount of heat, andare quite widely separated, danger of excessive heat localization, which might injure the insulationor the cabinet4 fin'- ish', is,-avoided. v f

The bus-connection'59, asshown in Fig. lb is adapted to be connected to the positive side of the farm current system through one blade of a plug` 62,y preferably of the polarized type, and the negativesides of the filament circuits of the detector and audio-frequencyl amplifier tubes are grounded to the set shielding, vfrom'which the filament circuit is completed as hereinafter described. To provide forfadequate and simple volume control the negative sides of the laments of the three radio-frequency Vamplifying ltubes are connected together and the common ylead 63 therefrom is carried through the variable volthe variable units v'described ume controlling resistance 20, Fig. 1,v the oppo -mon positive C and negative B lead 64.,V are preferably carried in a single cable provided at its end with a connector strip 65 adapted to bev attached toa combined B and C power unit only in such manner as will properlyy connect to the set, all the B and C power connections simultaneously, as described in my U. S., Patent No. 1,901,272,7granted March; 14, 1933.v

rThe lead 66 from the negative side of the farm-power circuit, andthe lead 64 from. the negative side of the B power supply and the positive side ofthe C powerfsupply are isolated from the receiver bythe olf and on switch 67, and accordingly when this switch 67 is in off or open position, all current supplying circuits of my system are broken, including the circuit for energizing the field coil of the dynamic speaker, the positive lead 6 8 of which is connectedto the positive side of the farm-power circuit inside the receiver and the negative lead 69 of which is grounded to the set shield, thus necessitating closure of the switch 67 4to complete the negative Aside of its circuit.

In case of excessive arcing in the switch 67 due to the inductive effect of the eld coil of the speaker, the switch 67 may be bridged by a suitable condenser as is well known in the art.

As above noted the farm power system illustrative of systems to which my invention isvparticularly applicable usually comprises aV storage battery and charger therefor and from rseveral hundred to several thousand feet-of power lines, and is usually ungrounded. Y

According to my invention this entire system is used as a filament loop, or counterpoise connected in the filament circuit of the receiver, and the resulting .greatpick-up of radio-frequency current enables my receiver to be operated with very little drain of B current, so that dry-cell battery units may be satisfactorily used to supply the B current for the receiver'.

Referring to Fig. l, the common filament current leads 59 and 66, as above noted, are connected `by means of the polarized plug 62 with the positive and negative lines, respectively, of the farm-power` system generally indicated by the with Ysubstantially no diminution, an untuned loopy or counterpoise is formed, and the'switching on or-oif of anyl lamp-71 hasno appreciable effectupon the transmission of radio waves picked up thereby to the. receiver. f

I have found that under all conditions, using this lament loop according Vto myV invention, when the farm power system isungrounded, extremely great` pick up of radio waves is effected even without the use of any antenna. or earth connection, particularly when the, point of "connection of the plug 62 tothe system'Y is considerably removed from the battery and charger unit thereof. In some instances, Vparticularly when the connection of the plug 62 Vto the system is quite proximate to -the battery andchargerkunit. i. e.,` within a few feet thereof, IV have found it advantageousto supplement the pick-up ofthe filament loop :by connecting `tothe post 72 (Fig. la) in the grid circuit of the first radio-frequency tube 12, a short antenna or an earthing lead. If the farm-power system is of the ungrounded or unearthed type, as is usually the case, it seems immaterial whether the post 72 be connected to an aerial or to earth, but if the system is earthed, either by design or through accident, I find that somewhat better results are obtained by the use system or the like as the filament loop, with or without a short `antenna or an earthing lead connected to the post 72, in itsbroad aspects Vmy invention includes .the use in my receiving system of a grounded lament loopwith or without .the use of a short antenna connected to post 72, and while I prefer to utilize the lament loop alone, locating the connection of the receiver thereto at a considerablev distance from the battery and charger unit, as shown, in its broad aspects my invention is notlimitedin this respect.; f

As above noted, the screengrids of the three radio-frequency amplifiers are, according to my invention, interconnected without suppression, so that the full effect and advantage rof the screen-grid system can be utilized; I am enabled to avoid suppression-vof the Yscreen-grid currents because of the fact that the great radio wave interceptive power of -the farm-power wiring employed as a filament loop lenables me to operate theiseveral amplifying tubes ofV my receiver at a greatly reduced plate potential without sacrifice of sensitivity, and in yaddition to these advantages `enables -me to reduce the plate current drain of the entire receiver 'to the order of9 milliamperes of current (using 84 volts maximum `plate potential) l thus -producing a seven tube screenY grid receiver, which can be successfully operated over long periodsoftime on a single set of dry cell B.batteries, an -advantage which has never heretofore been accomplished so far as I am aware. .Y My receiving system maybe successfully operated using ordinary B batteries and the-ordinary C`I battery for grid biasing, but `l; prefer, when-using B vand Cbatteries, toemploy-a special Bf and 0" power unit adapted to be connected directly to the-connectorl strip 65,v as shown in Fig. 1b, and fully disclosed in myv above mentioned Patent No.Y 1,901,272,` as the use Yof such unitinsures that vbefore failure of the unit '-1 substantially all the effectivelife of substantially all the cells will have been made use of, in contradistinction to the ordinary tapped B unit in which the cells drawn upon by the detector and amplifier tubes become exhaustedlong before the entirelife of the cells drawn upon by the amplifier tubes alone has been served. Moreoven my unit construction insures replacement of all the B and C battery supplies at the same time, which is essential forthe best results with the receiver.

It is clear fromthe above description that vthe ultimate result ofthe several improvements comprised in.my vinvention is the production of a greatly improved radio receiver capable of long and very efcient service where city power circuits are not available, and. one in whichrever'y. detail is so arranged as to present-noftechnical problems to the lay user as to how certain connectionsshould be made and whether or not certain of the B or C power. supplies should be replaced or retained. i

Having described what I consider .to be the best embodiments of my invention, I wishv it to be distinctly understood, however, that the spelll() its radio-frequency -wave yintercepting *means constituted substantially entirely byY said` lament-including closed loop.

n2. A fiilam'ent loop radio receiving system, saidl l system comprising a source rjofdirectv cur rent,- power conductors leading therefrom, 'a' shielded radio kreceiver embodying therrnlonic vacuum tubes vwiththe filaments thereof connected at one side to the receiver shielding,'al `connection-from one of said power conductors to'said receiver shielding', connections from the lother powerconductor to the other sidesof said i'lla-` mentsfor energizing the same `from said source oi? direct current, f saidV laments, connections,

conductors and source of direct current forming a y closed loop coupled to said receivei'fessentially by way of the direct inclusion of saidl filaments,

as distinguished from separatecapacity coupling, the radiofrequency vwave intercepting" means of the systeml beingY constituted essentially byY said lament-includingkclosedfloop.

3; A-y filament-loop radio receiving system, K

said system'comprising avradiov receiver embodying a plurality of thermionic vacuum tubes com-i prising therr'non'ic radio-*frequency amplifying,

thermionic detecting, andthermionic audio-fre-V quency'amplifying elements, an externalsource ofcurrentrand power 'conductors leadingv there# froml, meansy includingv separate "resistors lindividually connecting the filaments of said vacuum tubes at one side lthereofy to one ol' said power conductors, means connecting the otherr terminals of said detecting and audioffrequency am# plifying tube filaments directly totheother of saidv `power conductors, and'volume controlling means Aconnecting the `Aother terminaIsofsaid radio-frequency" amplifying tube illarnents to saidV other power conductor, said filaments,` con# necting means, conductors and current lsource forming av closed loop coupled to said reeciver essentiallyby way of the directinclusion of said llamen'taas distinguished from separate capaci` ity coupling, said system having its kradio-fre` duencywave intercepting means constituted essentially by said filament-including closed loop;

4. A filament-loop radio*y receiving system, said systemY including a receiver comprising athermionic vacuum tube havingV ak iilament, an

LVe'xternalsource of current and power conductors maan-s coupling', the-radiofre'quency energy lintercepting `means of-said'system being constituted essentially by said filament-including closed loop.

5, In'a radio receiving system, a shielded radio receiver embodying a'detector, `radio-frequency, and audio-frequency; vacuum tubes having -laments,` one? side of which is connectedto said shielding, land vplates connected to the positive B- potential leads, at leastonel of said audio-V frequency tubeshaving its grid return connected toga source of negative C biasing potential, a

pair'- of farm lighting conductors having aA potential diierence materially ygreater than vthe rated iilamentV voltageof any one of said laments, an individual voltage dropping resistance connected in-series with the other'end of each one of said filaments andconnected to one of said pair of farmlightingconductors, each of said individual resistances being of such value as to reduce the maximum farm-lighting conductor potential difference tothe maximum rated lament potential .merit, fB, -C{ and loud speaker fleld circuits.

6'. AIna radioreceiving system, a shielded radio recever'embodying a' detector radio-frequency, and audio-frequency vacuum tubes having laments, one side'foi which is -connected to said shielding, and plates connected tothe positive B potential leads, a pair of farm lighting conductors having f a potential l difference materially greater'than the lrated larnent voltage' of any i oneof` said filaments, an individual voltage dropping, resistance connected in series withthe other endr ofeach one of said lamentsand y'connected tov one 'of said pair ofr farm lighting conductors, each of -said individual resistances,being1 of such value as to reduce' the maximum farm lighting conductorl potentiajljrdiifer'ence tothe maximum rated iilament potential rof the-filament to' which it is connected, a: `'separate variable resistance interposed in rtheconnections from said radiofrequency `tubes to'said shielding, a loud speaker embodying ar eld circuit with leads extending therefrom, saidtileld circuitleads vconnected respectively tothe above mentioned vone of said pair of l farmlighting conductors and yto vsaid shielding; thepther of said farm; lighting conductors, together with the negative B potential lead 'being connectedl through a single switch the opening` of whichfeflects the 'breaking of the lament, B and loud speaker ileld circuits.

LYSLE G, 'rATRo. 

